1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a method for fabricating a capacitor in a semiconductor device, in which oxidization of upper and lower electrodes and wiring films is prevented during annealing a capacitor dielectric film for improving device characteristics.
2. Background of the Related Art
Methods for increasing a capacitance by forming a three dimensional capacitor electrode of a dielectric film of, such as SiO.sub.2, NO(Si.sub.3 N.sub.4), Ta.sub.2 O.sub.5, etc., have come to a limit as a semiconductor device packing density increases in a geometrical series. Recently, a method using a material of a high dielectric constant, such as BST (Barium Strontium Titanium Oxide), and PZT (Lead Zirconium Titanium Oxide) as the dielectric film has been suggested. The dielectric film of a high dielectric constant can lower fabrication costs and improve device reliability. However, because a direct deposition of the dielectric film of a high dielectric constant on a silicon substrate forms a silicon oxide film at an interface, which reduces total charge sharply, films with an excellent acid resisting property, such as Pt or Ir are used as the upper and lower electrodes of the dielectric film of a high dielectric constant. However, such use of Pt and Ir acts as a factor increasing product cost, since the Pt and Ir are not only expensive, but also difficult to use in fabrication processes, such as etching and etc. Moreover, since the electrodes of noble metals act as catalytic that decomposes H.sub.2 molecule, which flows in an ILD(Inter Layer Dielectric) process or an IMD(Inter Metal Dielectric) process, into H atoms, the electrodes of noble metals accelerate degradation of the dielectric film of a high dielectric constant. Those methods for fabricating a capacitor of a dielectric film of a high dielectric constant in a semiconductor device have the following problems.
The degradation of the dielectric film caused by catalytic effect of the upper and lower electrodes of the capacitor deteriorates device reliability. The degradation of the dielectric film occurs, not only in the ILD or IMD process, but also in H.sub.2 forming process by a flowing H.sub.2 gas conducted for decreasing resistivity and improving transistor characteristics after a wiring process.